This invention relates to a walking beam conveyor and more particularly to a walking beam conveyor for the intermittent movement of articles along a curved or linear transport path and is particularly suitable for moving heavy high-density loads and a method for operating such an apparatus.
Walking beam conveyors are provided for use in a wide variety of manufacturing machines and processes. For example, walking beam conveyors are used to support and move heavy articles along a transport path by lifting the article from an initial or first position at a first actuating station, transporting it to a second position, lowering the article so that it is supported in a stationary position at a second actuating station and returning to the first position to lift another article at the first actuating station while also lifting the article at the second actuating station and move both of those articles along the transport path. Such articles may be coils of sheet material, such as steel and the like, having a weight of many tons.
Of course, it will be appreciated that the walking beam type conveyors of the present invention disclosed herein are exemplary in nature and that the invention is not limited to use in steelmaking or handling generally. The walking beam conveyor and method of the present invention may be applied in any of a wide variety of applications which require movement of an article or articles along a linear or curved path to achieve the ends of a given manufacturing process or operation.
Walking beam or reciprocating conveyors for progressively moving an article along a linear path are well-known in the prior art (U.S. Pat. No. 4,219,113).
Some of these devices provide for the use of cams and linkages to raise, lower, and move the walking beam. U.S. Pat. No 4,928,811 provides a walking beam using a combination of Scotch yoke linkage and cam rollers to advance an article along a path. The use of a single motor is provided to drive a walking beam both along the transport path and to raise and lower the articles is provided but a very complicated linkage and beam system is required. U.S. Pat. No. 5,653,392 provides an accumulating conveyor system which raises and lowers a beam by means of a motor driven cam connected to a linkage which moves the beam in an vertical direction and supports the beam so that it can move along the linkage. Another cam-linkage device is disclosed in U.S. Pat. No. 4,040,514.
Other known devices provide for the use of ramps to raise and lower the walking beam. U.S. Pat. No. 4,919,254 provides a walking beam apparatus which supports the beam on ramps to move the beam in a vertical direction as it moves in a horizontal direction. The use of a flexible drive transmitting member such as a cable or chain is used in conjunction with ramps to provide a walking beam furnace so that the walking beam can be lowered beyond its operative stroke to a maintenance position as shown in U.S. Pat. No. 4,466,792. Another patent showing a walking beam furnace using ramps is shown in U.S. Pat. No. 4,330,262 for ready maintenance of a walking beam furnace.
Jacks have also been disclosed for raising and lowering the walking beam in U.S. Pat. No. 4,270,655. Air lifting units to raise and lower the walking beam are disclosed in U.S. Pat. Nos. 4,219,113 and 4 071,137.
It is desirable to provide a simplified linkage and mechanism to raise and lower a walking beam. It is also desirable to provide simplified crank arm geometry for raising and lowering a walking beam. It is further desirable to create the vertical lift motion of the walking beam with one lift cylinder. An additional desirable feature is to mount the vertical driving device, such as a lift cylinder, as close to the top of the walking beam as possible. Such a design allows for simplified maintenance and also improved control since synchronizing the flow control of the fluid used to move the cylinder is not necessary, such as in the case when two cylinders are used. Such desirable features also provide a walking beam conveyor that is easily and efficiently manufactured, installed and maintained.
It is also desirable to provide a linkage design that maximizes the force for raising and lowering the walking beam. Such a feature allows for greater loads to be raised and lowered by the walking beam with vertical lifting devices requiring less space.
It is desirable to provide for easy maintenance of the driving mechanism for a walking beam conveyor and also to protect the mechanism from physical damage and contamination by dust, dirt or other foreign particles. By providing quick access to the drive mechanism without removing or disassembly of the walking beam conveyor, maintenance time is minimized and also the possibility of incorrect reassembly of the walking beam after the maintenance is completed. This feature is important since downtime for maintenance or repair of the walking beam conveyor and consequently the entire production line is decreased.
It also desirable to provide a maintenance hood which acts as a structural member to support the articles as they are supported by the walking beam conveyor and moved between the stations. Such a maintenance hood allows mounting of a vertical driving device, such as a lift cylinder, as close to the top of the walking beam as possible. Such a maintenance hood also allows for flexibility in the positioning of the drive mechanism and more efficient design utilization of the space required for the linkage in the walking beam conveyor. It is also desirable to provide quick access to the vertical lifting device for maintenance.
It is also desirable to minimize the space required by lift mechanism to raise and lower the walking beam in a linkage used to raise and lower a walking beam. It is desirable to provide pivotal connections which have ease of maintenance and decreased manufacturing costs. It is desirable to provide a linkage to raise and lower a walking beam which allows the wheelbase or distance between wheels on each side of the walking beam be varied depending various design configurations of the manufacturing operations in which the walking beam conveyor is used. It is further desirable to simply change the wheelbase of a walking beam conveyor by simply changing the length of connecting links.
The present invention provides a walking beam conveyor and a method for operating such an apparatus with the above described desirable features that may be implemented in a wide variety of walking beam conveyor designs.
The walking beam conveyor of the present invention provides for the intermittent movement of articles along a transport path. Fixed holders are positioned along the transport path to temporarily receive the articles to be advanced. These fixed holders provide a series of actuating stations at spaced apart locations along the transport path to temporarily receive the articles as they are advanced along the transport path. The walking beam conveyor provides for movement of the articles between the actuating stations and includes a first and second set of rollers which are supported by a support surface with the rollers movable their along. Support links are pivotally secured to each of the rollers about the rotational axis of their respective rollers and connecting links are provided to interconnect the support links and thereby substantially synchronize movement of the support links, accordingly creating the lift motion of the walking beam.
The present invention provides a beam which is pivotally secured to the support links and is consequently supported by the rollers for movement along the transport path. Each set of rollers include a roller positioned on each side of the beam. The beam extends between the actuating stations. The beam has movable supports secured thereto for receiving and supporting the article as it is moved between the actuating stations.
The linkage of the present invention allows for the use of a single hydraulic cylinder to move the beam between an article supporting or raised position, in which the article is supported by one of the movable supports on the beam, and a retracted or lowered position in which the article is supported by one of the fixed holders at an actuating station. The hydraulic cylinder has one end connected to the beam and the other end pivotally connected to one of the support links so that upon actuation of the hydraulic cylinder, the beam is moved between the article supporting position and the retracted position. A crosslink is provided to pivotally connect the support links on each side of the beam to the hydraulic cylinder. Upon actuation of the hydraulic cylinder, the support links are rotated to consequently move the beam between the article supporting position and the retracted position.
The ratio of the distance between the rotational axis of the roller/support link and the pivot point connecting the beam to the support link and the distance between the rotational axis of the roller/support link and the pivot axis where the support link connects to the hydraulic cylinder is from between 1:2 to 1:3. It has been found that this ratio is preferred to provide sufficient lifting force on the beam and the vertical travel of the beam within the physical and design parameters required to achieve other favorable features of the present invention.
A drive motor is provided to move the beam along the support surface and consequently move the articles between the actuating stations. A maintenance hood is provided for covering the hydraulic cylinder during normal operation of the walking beam conveyor of the present invention. The maintenance hood is movable between a covering position, in which the hydraulic cylinder is covered during normal operation of the walking beam conveyor, and an open position in which the hydraulic cylinder may be maintained.
The present invention provides the desirable feature of providing a simplified linkage, mechanism and crank arm geometry to raise and lower a walking beam. The vertical lift motion of the walking beam is created with one lift cylinder which is mounted close to the top of the walking beam. By using one lift cylinder simplified maintenance and also improved control is provided by the present. The walking beam conveyor is easily and efficiently manufactured, installed and maintained.
The present invention provides a linkage design that maximizes the force for raising and lowering the walking beam which allows for greater loads to be raised and lowered by the walking beam with a vertical lifting device requiring less space. Accordingly the size of the lift cylinder may be optimized to thereby minimize the cost of manufacture.
The maintenance hood of the present invention and the mounting of the lift cylinder close to the top of the walking beam, provides for easy maintenance of the lifting device and also protects the mechanism from physical damage and contamination by dust, dirt or other foreign particles. The maintenance hood also provides quick access to the drive mechanism without removing or disassembly of the walking beam conveyor, and maintenance time is minimized as is the possibility of incorrect reassembly of the walking beam after the maintenance is completed. Such a design feature is important since downtime for maintenance or repair of the walking beam conveyor and consequently the entire production line is decreased. The maintenance hood also acts as a structural member to support the articles as they are supported by the walking beam conveyor and moved between the actuating stations.
The maintenance hood of the present invention allows for mounting a vertical driving device, such as the lift cylinder, as close to the top of the walking beam as possible. Such a maintenance hood also allows for flexibility in the positioning of the drive mechanism and more efficient design utilization of the space required for the linkage in the walking beam conveyor. The design of the present invention minimizes the space required by the vertical driving device and the linkage used to raise and low lower a walking beam.
The walking beam conveyor of the present invention provides pivotal connections which utilize split bushings to connect some of the linkage members. The use of the split bushings allow for ease of maintenance and decreased manufacturing costs. The linkage of the present invention allows the wheelbase or distance between wheels on each end of the walking beam be varied depending on the various design configurations of the manufacturing operations in which the walking beam conveyor is used. This is achieved by simply changing the length of connecting links.
Other desirable features and advantages of the present invention will become apparent from a study of the following description and the accompanying drawings which are illustrative of the invention.